1. Field of the Invention
The present invention relates to a process and system for controlling the operation of the pump of a well.
2. Description of the Prior Art
U.S. Pat. Nos. 4,058,757, 3,953,777, 3,778,694, and 3,075,466 disclose and refer to pump off controllers for shutting down the pump of a well if a pumped off condition occurs. By pumped off is meant that the fluid level in the well drops such that the pump is not lifting as much fluid and, hence, the amount of work done by the pump decreases. Continued pumping under pumped off conditions may result in damage to the equipment. Thus, the pump is shut down for a time period sufficient to allow the fluid level to raise to a desired pumping level.
It has been observed that another condition other than a pumped off condition can occur in a well wherein the amount of work done by the pump is reduced from normal. In many cases, particularly in secondary recovery projects, protracted shut in periods of pumping systems will allow the fluid level to rise to a point that will reduce the amount of work at the polished rod sufficiently to make the well seem to be pumped off. The high fluid level essentially makes the well shallower. The pump is required to lift less head and, hence, the work done by the pump is reduced. This is not a condition where one desires to shut down the pump but rather a condition where one wants to continue pumping.
Present day pump controllers which look at the load on the pump or the amount of work done by the pump cannot distinguish this high fluid level condition or false pumped off condition from an actual pumped off condition. Thus, if a high fluid level is present upon start up, the controller will detect the false pumped off condition and shut the well in allowing the fluid level to raise further.
In order to allow the pumping system to automatically pump down the high fluid level and continue to operate in a normal manner, some provision must be made to distinguish between a high fluid level condition and an actual pumped off condition and to shut the well in only upon the occurrence of an actual pumped off condition.